In 2014, Altman was named president of Y Combinator, regarded as the best seed-stage accelerator in the world by its founders[3] as well as the most commercially successful.[4] Altman announced in a 2014 blog post that the total valuation of all Y Combinator companies had surpassed $30 billion, including well-known companies like Airbnb, Dropbox, Zenefits and Stripe.[5]

Altman has stated that he hopes to grow Y Combinator so that it eventually funds 1,000 new companies per year. He has also increased the types of companies funded by YC, especially on so-called "hard technology" companies. [6]

In July of 2015, Altman announced the YC Fellowship, a new program to give grants of $12,000 and advice to very early-stage startups. [7]

Altman was named the top investor under 30 by Forbes in 2015,[8] one of the "Best Young Entrepreneurs in Technology" by BusinessWeek in 2008[9] and listed as one of the five most interesting startup founders between 1979 and 2009 by his colleague Paul Graham.[10]

He was the CEO of reddit for 8 days in 2014 after the then-CEO Yishan Wong resigned.[13] As part of his investment, he developed a new way for the community to own part of the company. He announced the return of Steve Huffman as CEO on July 10, 2015.[14]